Cable type and selection calculation First, the definition and classification of cable The generalized wire and cable is also referred to as cable. Narrow cable is an insulated cable. It can be defined as a collection of one or more insulated cores, as well as their respective possible cladding, the total protective layer and the outer sheath. The cable may also have additional conductors that are not insulated.
China's wire and cable products according to their use are divided into the following five categories: 1. bare wire, 2. Winding wire, 3. Power cable, 4. Communication cable and communication cable, 5. Electrical equipment with wire and cable wire and cable the basic structure: 1. Conductor conduction current Of the object, the specifications of the wire and cable are shown in the conductor cross-section 2. Insulation of the outer layer of insulation material according to its tolerance voltage Second, the working current and calculation of electricity (line) cable operating current formula: single phase I = P ÷ (U (A) three-phase I = P ÷ (U × 1.732 × cosΦ) P-power (W); U-voltage (220V); cosΦ- power factor (0.8) W); U-voltage (380V); cosΦ-power factor (0.8); I-phase current (A) The general copper wire safety cut-off volume of 5-8A / mm2, aluminum wire safety cut-off capacity of 3- 5A / mm2. In the single-phase 220V line, the current per 1KW power in the 4-5A or so, in the three-phase load balancing of the three-phase circuit, the current per 1KW power in about 2A. That is, in a single-phase circuit, every 1 square millimeter of copper wire can withstand 1KW power load; three-phase balanced circuit can withstand 2-2.5KW power. But the greater the operating current of the cable, the smaller the safe current per square millimeter can withstand. Cable to allow safe working current formulas: ten under five (ten times multiplied by five) hundred on two (more than a hundred multiplied by two) two five five five three sector (two five times by four, three times by three) Nine and two and a half times (seven hundred and ninety five lines are multiplied by 2.5) through the tube temperature of eighty-nine fold (with the temperature changes, in a good number of safe current multiplied by 0.8 or 0.9 ) Copper wire to complete the calculation (in the same section of the aluminum core line to rise a level, such as 2.5 copper wire is 2.5 aluminum core line up a level, according to four square mm aluminum core line) Half (in the original safe current is based on the number of good plus half)
Cable Specifications Model Meaning: wire model: the letter B that cloth wire, the letter V that plastic in the PVC, the letter R that the cord (the conductor is a lot of twisted together). There are copper symbols, hard lines (common single-core conductor) symbols are not shown. Common cable type: BV- said single copper core PVC insulated wire, no sheath line. Applicable to AC voltage 450 / 750V and below power plants, household appliances, instrumentation and telecommunications equipment with the wire and cable.
, The power cable for AC 50HZ, rated voltage 0.6 / 1KV and below transmission and distribution lines for transmission and distribution of energy purposes. Ambient temperature 25 ℃, the cable conductor operating temperature does not exceed 70 ℃. VV (VLV) copper (aluminum) core PVC insulated PVC sheathed power cable, suitable for laying indoors, tunnels.